Medical gas humidification system

ABSTRACT

An apparatus and method for on-the-go humidifying an insufflation gas through water vapor transfer from a liquid to the insufflation gas through a barrier separating the gas from the liquid to enable the gas in a normally trauma inducing state to be brought to a conditioned state. If the gas is at an improper insufflation temperature the temperature of the gas can be brought to the proper insufflation temperature at the same time the gas is humidified through heat transfer through the barrier.

FIELD OF THE INVENTION

This invention relates generally to a medical apparatus and method and,more specifically, an apparatus and method for conditioning a gas sothat when the conditioned gas is delivered to a body cavity it preventsor minimizes additional trauma to a patients body then if the gas werenot conditioned.

CROSS REFERENCE TO RELATED APPLICATIONS

None

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

REFERENCE TO A MICROFICHE APPENDIX

None

BACKGROUND OF THE INVENTION

One of the problems during surgery occurs when a medical gas, which isused to insufflate a body cavity, produces additional trauma eitherdirectly or indirectly to the body. While the body must endure thetrauma produced by the surgery, the use of medical gas, which is oftenreferred to as an insuflation gas, can cause additional trauma to thebody resulting in cell stress or cell death. The trauma caused by themedical gas is due to the properties or state of the medical gas that isdelivered to the body cavity. For example, the temperature of the gas aswell as the moisture content of the gas can produce cell desiccation,cell stress, inflammation and cell death which can result in adhesionsas well as pain to the patient and consequently a longer recovery time.Ott et al. U.S. Pat. Nos. 5,411,474 and 6,068,609 recognizes that thecause of the additional trauma from if the medical gas is at an improperinsufflation temperature or if the medical gas is to dry when themedical gas is delivered to the body cavity.

The Ott et al. U.S. Pat. No. 6,068,609 discloses a device forconditioning the medical gas wherein water is injected into aheater/hydrator to increase the humidity of the gas as well as thetemperature of the medical gas.

The Ott et al. U.S. Pat. No. 5,411,474 discloses a further device forheating, humidifying and filtering insufflation gasses prior to andduring medical procedures.

The present invention comprises a method and apparatus using a fluid gasseparation barrier that permits water vapor and heat transfertherethrough but prevents liquid transfer therethrough to condition amedical gas by bringing the medical gas from a “trauma inducing state”,i.e. a state where the gas if introduced into a body cavity will causecell stress or cell death, to a “trauma free state” i.e. a state wherethe introduction of the medical gas into a body cavity does not causedamage to the cells of the body.

SUMMARY OF THE INVENTION

An apparatus and method capable of conditioning a medical gas byhumidifying the medical gas through transfer of water vapor from a fluidto the medical gas, which is constrained by a barrier, to enable themedical gas, which is normally in a “trauma inducing state” to beconditioned either statically or on-the-go to a “conditioned state” thatprevents or inhibits additional trauma to a patient when the gas in the“conditioned state” is introduced into a patient. The gas is brought tothe conditioned state through the transfer of water vapor through thebarrier, which extends as an interface separating the water and themedical gas. The barrier is permeable to water vapor transfer butprevents liquid water passage therethrough. In addition, if the medicalgas is not at the proper delivery or insulation temperature the medicalgas can be brought to the proper deliver temperature by conduction heattransfer through the barrier. The heat transfer and water vapor transfercan either be separately transferred or the barrier can be used tosimultaneously transfer both heat and water vapor to bring the medicalgas to the proper insufflation condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial schematic of a system for bringing a medical gasto a trauma free state before delivering the medical gas to a bodycavity;

FIG. 2 shows a cross sectional view of one embodiment of the deliverysystem;

FIG. 3 shows a cross sectional view of the outer fluid circulationpassages with the medical gas tube coaxially positioned therein;

FIG. 3A shows a cross sectional view of both the medical gas conduit andthe fluid circulation tube;

FIG. 4 is a cross sectional view of a medical gas humidification andheat exchange tube;

FIG. 5 is an end view of a medical gas humidification and heat exchangetube with multiple gas ports;

FIG. 6 is a partial side view of the medical gas humidification and heatexchange tube of FIG. 4;

FIG. 7 is a cross sectional view of the medical gas humidification andheat exchange tube with a heating element located on an exterior surfaceof a central gas duct;

FIG. 8 is a partial schematic diagram of a system for humidifying andheating medical gas;

FIG. 9 is an end view of a medical gas humidification and heat exchangetube with multiple passages therein;

FIG. 10 is a system for delivering a medical gas to an entry device withthe system including a chamber with a heating element for heating acontainer of water placed in the chamber of the system;

FIG. 11 is a cross sectional side view of a closed medical gashumidification and heat exchange system;

FIG. 12 is a partial cross sectional to view of the closed medical gashumidification and heat exchange system of FIG. 11;

FIG. 13 is a medical gas humidification system for increasing the watercontent of a medical gas through wicking of moisture into the gas;

FIG. 14 is an enlarged portion of a porous barrier for use in medicalgas humidification and heat exchange system with the barrier havingpores extending through the barrier to permit water vapor to passtherethrough; and

FIG. 15 is an enlarged view of a portion of a non porous barrier for usein medical gas humidification and heat exchange systems with thenon-porous barrier that permits migration of water vapor through thebarrier.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the system 10 of the present invention for eitherstatically or on-the-go delivering a medical gas in a trauma free state.The system 10 includes a source of medical gas 12, a filter 13, whichcan be used for removing contaminants from the medical gas, and anelongated tube 21 for delivery of the medical gas to an entry device 23.Attached to elongated tube 21 is a heater and pump 11 which circulates aheated fluid through conduit 11 a into an elongated flexible tube 21 andthen returns the fluid to the heater and pump 11 through conduit 11 b.The system is particularly useful in laparoscopic surgery although othertypes of surgeries requiring insufflation can benefit by the presentinvention which can prevent peritoneal cell damage, evaporation anddesiccation effects.

In the embodiment shown in FIG. 1 a control module 14 connects to thesource of medical gas 12 though lead 14 a to enable one to control therate of medical gas flowing into the elongated tube 21 by operation ofcontrols (not shown) in control module 14. Similarly, lead 14 b allowsone to control the heater and the pump 11 from the control module 14. Athird lead 14 c extends from a temperature sensor and humidity sensorlocated proximate the entry device 23 to the control module 14 to permitthe operator monitor the medical gas temperature and humidity andthrough use of the control module set or control the temperature and/orthe humidity of the medical gas entering a patient through the entrydevice 23. A commonly used medical gas which is used for insufflation iscarbon dioxide; however, the present invention is usable with other gasincluding air, nitrous oxide, argon, helium or mixture of gases.

In the system shown, a medical gas under pressure flows through apressure regulator or insufflator (not shown) and into an elongated tube21 and into a shutoff valve 24 which has an open and closed condition.With shutoff valve 24 in the closed condition the gas is prevented fromentering entry device 23 but with the shutoff valve 24 in the opencondition gas flows into entry device 23 which in the present embodimentcomprises a trocar sleeve and therefrom into a body cavity of a patient.In order to remove contaminates in the medical gas one can flow themedical gas through filter 13 to remove contaminants therefrom. As themedical gas flows through the elongated tube 21 both heat and water canbe transferred to the medical gas to bring the medical gas to a“conditioned state” when it arrives at the entry device 23.

As user herein the “conditioned state” is a gaseous state where themedical gas when introduced into a body cavity limits or inhibits cellstress or cell death due to the contact with the medical gas as opposedto gas in a “non-conditioned state” which can cause additional cellstress and cell death. While the exact conditions of the medical gasthat causes cell stress or cell death vary with the person as well asthe type of surgery it is understood that at certain humidity andtemperature conditions the physical properties of the medical gas causestrauma to the cells of the patient and consequently discomfort or painto the patient. On the other hand a “conditioned state” is a gaseousstate where the medical gas, when introduced into a body cavity, thateither does not damage the cells of the body or inhibits damage to thecells of the body as a result of contact with the medical gas in theconditioned state. The conditioned state occurs when the properties ofthe medical gas are such that the medical gas is at or close to bodytemperature and the relative humidity of the gas is sufficiently high soas not to produce cell stress or cell death. The exact conditions orproperties of the medical gas where the medical gas does not cause cellstress or cell death can vary with the type of tissue as well as manyother factors. As used herein, the condition where the delivery ofmedical gas does not cause stress or damages to the cell is referred toas a condition wherein the medical gas is in a “conditioned state” whenintroduced into a body cavity. The exact determination of when a gas isin a “conditioned state” can be determined by observation of the effectsof a medical gas on the patient; however, such field determination arenot feasible since it would cause injury to the patient. Consequently,for most applications maintaining the temperature of the medical gas ator about body temperature and the relative humidity of at the medicalgas of least 50% produces medical gas is in a “conditioned state” thatcan be delivered to the body cavity at either high or low flow ratewithout causing adverse effects to the patient or the cells of thepatients body as a result of contact between the gas and the patient'sbody. It should be understood, that although the gas in a conditionedstate that prevents or inhibits damage to the cells in a patient whenthe gas is in contact with a patients body the improper delivery of thegas to the patient body cavity can still cause trauma to the patient.However, the present invention provides that with proper delivery of theconditioned gas one can prevent or inhibit additional trauma to apatient. By proper delivery it is understood that the medical gas isbrought into contact with the patients body through slow moving gassesto avoid the “wind chill effect”.

A reference to FIG. 1 denotes the elongated tube 21 has a transferlength denoted by “L”. The distance “L” is the distance along the lengthof the tube 21 where both heat and water vapor can be transferredbetween a medical gas located on one side of a liquid gas separationbarrier such as a membrane and the fluid located on the other side ofthe membrane. The barrier of the present invention is permeable to watervapor transfer to permit humidification of the gas on the opposite sideof the barrier from the water in the tube 21 while at the same time thebarrier prevents liquid water passage through the barrier and into themedical gas. In addition, in the preferred embodiment the separationbarrier between the medical gas and the liquid water is formed from athermally conductive material to enable heat to be transferred betweenthe liquid on one side of the barrier and the gas on the other side ofthe barrier at the same time water vapor is transferred from one side ofthe barrier to the other side of the barrier. That is, the heat from afluid, which is at a higher temperature than the medical gas andnormally either above or equal to a normal body temperature (37° C.) isconducted through the barrier to heat the medical gas to the properinsufflation temperature, which in most cases is about normal bodytemperature as the gas lingers or flows into the transfer tube.

In addition to the heat transfer, water vapor from the fluid diffusesthrough the barrier to increase the water content or humidity of themedical gas. Thus the barrier or membrane serves a dual function in thatit permits heat transfer from the fluid to the medical gas as well asallow diffusion of water into the medical gas from the fluid therebyincreasing the humidity of the gas.

Nonporous membranes and porous membranes are known in the art.Typically, nonporous membranes generally comprise polymers that haveseparation properties based on the relative solubility and permeabilityof the molecular species of the polymer. Nonporous membranes allow masstransfer to occur thorough a solution diffusion mechanism where amolecule first dissolves into the polymer and diffuses through thepolymer from a region of high concentration to a region of lowconcentration. Since the chemical and physical nature of the moleculeaffects the solubility and diffusitivity, nonporous membranes canseparate mixtures of molecules. Nonporous membranes are typicallydesigned and manufactured to be free of pores that extend through themembrane wall, thus prohibiting a nonselective hydraulic transport ofliquid or gasses through the membrane wall. Typical, examples ofmaterials used to form nonporous membranes include polyvinylaccohol,cellulose, cellulose derivatives, nylon, polyesters, polycarbonates,polysulfones, polyethersulfones, polyimides, silicones andpolyurethanes. In general, nonporous membranes made from materials thatare more permeable to water vapor are preferred since they can reducethe size and cost of the device.

In the present invention one can use a nonporous membrane that permitswater molecules to diffuse through the membrane so as to be taken up ina gaseous state yet does not permit liquid water to hydraulically passthrough the membrane which would create a gas that contains both aliquid and a gaseous phase and therefore unsuitable for insufflationpurposes.

Porous membranes generally have separation properties based on therelative size of the molecules or particles of a mixture. For example,in the present invention one can use a porous membrane that permitswater molecules in the gaseous state to diffuse through the pores of themembrane yet does not permit liquid fluids to hydraulically passthorough the pores of the membrane which could create an insuflation gasthat contains both a liquid and a gaseous phase and therefore unsuitablefor insufflation purposes. If the pores of the membrane contain gas orwater vapor molecules and not liquids this condition is termed in themembrane art as a non-wetting condition.

In operation of a membrane in the non-wetting condition the pores of anon-wetting porous membrane do not become filled with liquid under apressure differential between the liquid on one side of the membrane andthe gas stream on opposite side of the membrane. In the case where theliquid is water, a hydrophobic porous membrane can be used. The degreeof hydrophobicity of the membrane is dependent on the size of the poreswith membranes of larger pore size requiring materials of lower surfacetension. However, to prevent the possible transfer of the bacteria fromthe liquid steam on one side of the membrane to the gas stream on theopposite side of the membrane a maximum pore dimension of about 0.2microns is preferred. Typically, materials suitable for the manufactureof a hydrophobic membrane include polyolefins, fluorinated polymers suchas tetrafluoroethylene or fluorinated ethylene-propylene,poplyetherimides, polysulfones silicones and other hydrophobic polymers.

While diffusion membranes are described herein other barriers can beformed from materials that permit passage of water vapor therethroughwhile preventing liquids from passing therethrough can be used. Thus amethod and apparatus utilizing a concentration gradient transfer methodcould be used to transfer the water vapor across a barrier.

A reference to FIG. 2 shows a cross sectional view of one embodiment ofan elongated tube 21. Elongated tube 21 comprises an outer annularmember 30 having a central tube 31 located coaxially within tube 21.Central tube 31 is a diffusion membrane that permits water molecules todiffuse therethrough but does not allow for direct flow of fluidtherethrough. A first elongated radial fin 32 extends from the exteriorcylindrical surface 31 a of tube 21 to the interior cylindrical surface32 a of tube 21. Similarly, a second elongated radial fin 33 locateddiametrically opposite from fin 32 extend from internal cylindricalsurface 30 a to exterior cylindrical surface 31 a of central diffusionmembrane 31 to divide the internal lumen of tube 21 into an upper lumenor fluid passage 35 having a generally semi circular cross sectionalflow area and a lower lumen or fluid passage 36 also having a generallysemi circular cross sectional flow area.

FIG. 3 shows a partial cross sectional view taken along lines 3-3 toreveal the interior fluid passages 35 and 36 of tube 21. Fluids, such aswater or in some cases water containing other materials that are to bediffused through the membrane enters fluid passage 35 though the fluidinlet 11 a and flows along passage 35 as indicated by the arrows. Thetube 31 and the elongated longitudinally extending radial fin 33 and 32cause the fluid to flow along the exterior semi-cylindrical surface 31 aof tube 31 until it is allowed to return along fluid passage 36 whichthen directs the fluid back to heater and pump 11 through fluid conduit11 b. In order to elevate the temperature of the medical gas to theproper temperature the fluid is heated in heater 11 to a temperatureequal or in excess of the desired medical gas temperature to enableconduction heat transfer from the fluid stream in passages 35 and 36 tothe medical gas in the central tube 31.

FIG. 3A shows a cross sectional view of a portion of elongated tube 21in cross section as well as a cross sectional view of internal membranetube 31, which is a tube with a circular shaped cross section that hasbeen formed from a diffusion membrane. In the embodiment shown thefluid, which is heated by pump and heater 11 flows into fluid passage 35located along one side of the tube 31 until it reaches the end of theelongated tube 21 where an opening in the radial fin (not shown) allowsthe fluid to enter fluid passage 36 where it flows along passage 36until the fluid is directed through outlet port 11 b and back into theheater and pump 11. As the fluid flows back and forth along the exteriorsurface of membrane tube 31 two events occur. First, as the fluid has ahigher heat content then the medical gas the gas temperature quicklyincreases toward the temperature of the fluid in the fluid passages.Second, the membrane tube 31 permits water molecules to diffuse throughthe sidewall of the membrane tube 31 to increase the gaseous moisturecontent of the medical gas therein without allowing water orcontaminants to flow directly into the medical gas. A temperaturesensor/and or humidity sensor 37 is located on the interior of themedical gas conduit 31 with a lead 14 c extending therefrom to thecontrol module 14 (FIG. 1) to permit an operator to monitor thetemperature and the relative humidity and thus be in a position tocontrol either the temperature of the medical gas delivered to the entrydevice 23 (FIG. 1) or the humidity of the medical gas delivered to theentry device or both.

In the present invention the inner tube 31 comprises a diffusionmembrane that permits diffusion of water vapor from the fluid in chamber35 into the lumen or gas passage 39 where the medical gas is flowing yetdoes no permit direct flow of liquid water therethrough which mightrender the medical gas unsuitable for use. In the present invention, themedical gas is normally at room temperature and is primarily heated byconduction as heat flows from the hotter fluid through the annularmember 31 and into the medical gas in gas passage 39 thereby elevatingthe temperature of the medical gas to an acceptable delivery temperature(usually in the 35° C. to 38° C. range). By simultaneously supplyingboth moisture and heat to the medical gas one can quickly bring themedical gas to a “conditioned state” before the medical gas dischargesfrom the elongated tube and enters the entry device 23.

In the present invention one can maintain the medical gas in aconditioned state through the use of an extended interface that forms anextended heat transfer region produced by the coaxial positioning of theinner medical gas tube 31 within the interior of outer fluid tube 30.

For various medical procedure there exists a range of flow rates(designated herein by Q) required to maintain a body cavity in aninflated or insufflated condition. In order to maintain the fluid in a“conditioned state” as the gas discharges from the elongated tube 21 andenters the entry device 23, the membrane tube 31 should have aninterface region that is sufficiently long and has sufficient transferarea so that there is sufficient heat transfer from the fluid at amaximum flow rate Q_(max) to maintain the temperature of the medical gasat a constant suitable delivery temperature at the entry device 23. Thatis, as the flow rate Q of medical gases decreases the fluid mightrequire less heat to maintain the medical gas at the proper deliverytemperature and conversely at the higher flow rates the medical gasmight require more heat transfer to maintain the medical gas at theproper temperature. Thus, through the mechanism of heat transfer, whichoccurs substantially through conduction, across an extended diffusionmembrane 31 one can bring the temperature of the medical gas to anacceptable delivery temperature at the entry device 23 and one canmaintain the medical gas at the acceptable delivery temperature eventhough the flow rate of medical gas through the elongated tube and intothe body cavity can fluctuate. Thus, the present invention smoothes outvariations in gas delivery temperature since the temperature of themedical gas discharged into the entry device 23 can be maintained at arelative constant acceptable delivery temperature by controlling thevelocity and temperature of the fluid flowing in outer fluid passage. Ifdesired, information from the temperature and humidity sensor 37 can beused to automatically control the flow rate of fluid thought a feedbackcontrol system.

Similarly, by having sufficient surface area between the fluid stream inlumen 35 and 36 and the medical gas in lumen 39 one can diffusesufficient moisture into the medical gas to maintain the relativehumidity at a minimum level. That is, the elongated tube permits thediffusion of water through the membrane and is sized so that at themaximum flow rate Q_(max) the amount of water that can diffuse throughthe membranes is sufficient to maintain the relative humidity above apredetermined amount.

While the system has been described as an on-the-go delivery of amedical gas in a conditioned state it will be understood that the systemis also usable in those conditions where the on-the-go heating andhumidifying of the medical gas is not required.

Thus the invention comprises a system for conditioning a medical gas tobring the medical gas to a conditioned state when delivered to a bodycavity with the system including a source of medical gas 12, anelongated coaxial tube 12 having an internal medical gas conduit 31 anda set of exterior semi circular fluid conduits 35 and 36 with themedical gas conduit 31 having a sidewall comprised of a diffusionmembrane. The medical gas conduit has an outlet (not shown) fordischarging a heated and humidified medical gas into an entry device 23.In order to transfer heat and moisture to the medical gas the fluidpassage includes a fluid inlet to the fluid conduit and a fluid outletin the fluid conduit to permit circulation of the heated fluid to raisethe temperature of the medical gas in conduit 31. In order to monitorthe state of the gas a medical gas temperature sensor and/or humiditysensor 37 is located on the interior medical gas conduit 31 (FIG. 3A) tomonitor the temperature and/or humidity of the medical gas dischargingfrom the medical gas outlet. To maintain the fluid at the propertemperature a pump 11 circulates the heated fluid through an outer fluidconduit so that when the medical gas is delivered through the internalmedical gas conduit the fluid circulating through the outer fluidconduit simultaneously raises both the temperature of the medical gasand the humidity of the medical gas to a body deliverable state thoroughtransfer of both heat and water through membrane 31.

While the present invention discloses a membrane that extends along thelength of a cylindrical delivery tube it is envisioned that other shapesinterface chambers can be used with the present invention along as thereis sufficient membrane interface area to transfer either heat ormoisture to the medical gas. As the medical gas is in non-dispersivecontact with the water or fluid the membrane prevents transfer oforganic or inorganic agents that could contaminate the gas stream. Afurther benefit of the invention is that the heat and water aredistributed more evenly during medical gas flow which can be continuousor intermittent. This results in the gas within the medical gas tubebeing held at a substantially constant temperature and humidity leveleven during conditions of no gas flow. In addition, the humidificationprocess is a continuous process since the water is on one side of themembrane and the gas on the other side whether or not either the gas orthe water is flowing in the system. A further benefit is that if onewants to maintain the humidity of the medical gas at 100% withoutcondensation the diffusion barrier is self limiting in that water vaporwill not transfer through the membrane if the medical gas is saturatedwith water vapor.

In the present invention both heat and moisture are transferred thoughthe membrane. It is envisioned that if the medical gas is at the properbody delivery temperature one need only use the membrane to transfermoisture into the medical gas.

FIG. 4 is a cross sectional view of an alternate embodiment a medicalgas humidification and heat exchange tube 50 that can be inserted into asystem to bring the medical gas to the proper delivery state. Tube 50includes an outer cylindrical tube 52 and an inner cylindrical tube 51which is centrally held in the lumen of tube 52 by a first annular plug53 located at one end and a second annular plug 54 located at the otherend. The gas tube 51 includes an open end 51 a for introducing a medicalgas therein. In operation, the medical gas, which can be in an improperinsufflation temperature and improper insufflation humidity state,enters tube 51 a and flows through tube 51 and discharges at end 51 b(indicated by arrows). When the medical gas is discharged from tube end51 b the medical gas is at the proper insufflation temperature and theproper insufflation humidity.

The humidification of the medical gas in tube 51 is accomplished thoughdiffusion of water vapor through the annular barrier wall of tube 51.That is, located around the gas tube 51 is a fluid chamber 57 having aninlet 55 at one end and an outlet 56 at the other end. In the embodimentshown the water entering inlet 55 is at the desired delivery temperatureof the medical gas. As the medical gas flows along gas duct 51 watervapor and heat transfer occurs. The humidity or moisture content of themedical gas can be increased to the proper level while at the same timethe medical gas can be heated or cooled to the desired deliverytemperature at gas outlet 51 b through conductive heat transfer throughthe barrier wall of tube 51.

FIG. 5 is an end view of an alternate embodiment of a medical gashumidification and heat exchange tube 60 which is similar to the heatand humidification tube of FIG. 4 except the heat and humidificationtube 60 instead of having a single central gas port has multiple gasports 62 located in a lumen 63 with the fluid passage formed by theexterior surfaces of the gas ports 62 and the inner cylindrical surfaceof conduit 61.

FIG. 6 is a partial side view of the medical gas humidification and heatexchange tube 60 of FIG. 5 revealing the end plugs 63 and 63a supportingthe multiple gas ducts or tubes 62 therein while gas flows therethrough.The sidewalls of the tubes 62 comprise a barrier to that preventspassage of liquid water into the stream of medical gas in tubes 62 yetpermit passage of water vapor therethrough. In operation, the medicalgas humidification and heat exchange tube 60 is connected to a source ofmedical gas on the inlet end and to a device such as entry device on theopposite end.

FIG. 7 is a cross sectional view of the medical gas humidification andheat exchange tube 70 having a resistance heating element 76 locatedaround an exterior surface of a central gas duct 79. The gas ductsidewall comprises a barrier to passage of liquid therethrough butpermits transfer of water vapor therethrough to humidify the gas in thegas duct In the embodiment shown the heating element connects toexternal electrical leads 77 and 78 which can be connected to a controlsystem to maintain the temperature of the water in the chamber 75 at theproper temperature.

As envisioned with the devices of FIGS. 4-7 one can incorporate themedical gas humidification and heat exchange tube directly into thesystem between the source of medical gas and the device for deliveringthe medical gas into the patient.

FIG. 8 is a partial schematic diagram of a system 80 for humidifying andheating medical gas. The system includes a water source 81 with aheating element 87 therein, a medical gas source 83, a heat and moistureexchanger 82, a pump 85 and a control module 86. In operation of thesystem the pump 85 forces water through passage 81 b and directs thewater into the heat and moisture exchanger 82. The water then flows inpipe 81 a into the water source 81 where the temperature of the water ismaintained for recirculation. A control module 86 allows one to increaseor decrease the temperature of the water as well as to control the flowrate of the medical gas. The medical gas 83 enters the heat and moistureexchanger 82 wherein heat is transferred to or from the medical gasthrough conduction and moisture is added to the medical gas throughdiffusion before the medical gas discharges into the patient thoughinsufflation conduit 84.

FIG. 9 is an end view of an alternate embodiment of a medical gashumidification and heat exchange tube 90 with a daisy like set ofmultiple radial gas passages 93 formed by an inner fluid conduit 91. Theembodiment of FIG. 9 provides a larger surface area between the twofluids per unit length to enable more rapid transfer of heat and watervapor therethrough. Fluid conduit 91 is formed from a material that is abarrier to liquid passage but permits water vapor transfer therethrough.In the embodiment shown in FIG. 9 the inner conduit 91 can be centrallysupported by radial struts 90 d, 90 b and 90 c. In operation theembodiment of FIG. 9 a fluid such as water can flow in the passage 92located between inner surface 90 a and outer surface 91 a and theinsufflation gas can flow in the radial gas passages 93. The fluid canbe used as the heat source as well as the water vapor source to transferheat to and from the medical gas in the radial gas passages 93 to bringthe medical gas to the proper insufflation temperature (about 37° C.).Although the central lumen 93 is shown as the insufflation gas passageit is envisioned that the outer lumen 92 could also be used as theinsufflation gas passage and the inner conduit used as the fluidtransfer conduit. Such an arrangement is well suited to thoseapplication where only water vapor transfer across the barrier isrequired to bring the insufflation gas up to the desired humidificationlevel.

FIG. 10 is an alternate embodiment of system 100 using a heat andhumidification exchange tube 105. In system 100 a medical gas at propertemperature and humidity is delivered to an entry device 112 with thesystem including a chamber 101 with a heating element 102 for heating acontainer of water 108 which is placed in the chamber 101 a. In theembodiment shown a sealed pouch 108 containing a fluid is placed inchamber 101 a. A first tube 106 having a pointed pouch piercing end 106a and a second tube 103 having a pointed pouch piercing end 103 aprojects upward into the chamber 101 a. In operation of the system aflexible skin pouch or other type of punctureable container 108 isforced onto the pointed ends 106 a and 103 a causing penetration of thecontainer 108. The container can be made of resilient material thatseals around itself as the pouch is punctured. Once the tubes 103 a and106 a are inserted in the pouch the fluid can be circulated to and fromthe pouch through tubes 103 and 104.

Tube 103 connects to the medical gas humidification and heat exchangetube 105. A pump 104, which could be a peristaltic type pump, drawsfluid into tube 103 and forces fluid out tube 106. The medical gassource 110 delivers the medical gas to the medical gas humidificationand heat exchange tube 105 through passage 111. The medical gashumidification and heat exchange tube 105 brings the temperature of thegas to the proper deliver temperature by conduction heat transferthrough a sidewall of a gas passage and to proper humidity by transferof water vapor through the sidewall of the gas passage.

While the embodiments of the heat and humidification exchange membersare shown as tubes, FIG. 11 and FIG. 12 show a cross sectional side viewof another embodiment of a medical gas humidification and heat exchangesystem 120. System 120 comprises a housing 121 having a water vaporpermeable member 126 forming the bottom of a fluid chamber 123. Locatedin fluid chamber 123 is a heating element 124 that has electrical leads125 that extend outward for connection to a source of electrical power.A vent cap 122 allows one to fill the chamber 123 with a fluid such aswater. Located below water vapor permeable member 126 is a gas chamber128 having an inlet 127 and an outlet 128. In the embodiment shown thelarge volume of the fluid chamber 123 and the medical gas chamber permitcontinuous heat and moisture transferred to the medical gas throughoutthe surface area of the barrier 126 that separates chamber 124 fromchamber 129. In this embodiment the moisture and heat transfer isaccomplished through the use of a flat compact barrier or the like asopposed to an elongated tube.

FIG. 13 is a medical gas humidification system 130 for increasing thewater content of a medical gas through wicking of moisture into chamber137 followed by evaporation into the gases state. System 130 includes aclosed chamber 135 having a medical gas inlet 131 and a medical gasoutlet 136 with a chamber 137 located in the enclosure. A wick 132extends through the wall and into a container 133 having water 134therein. In operation of the system shown in FIG. 13 the medical gasenters the chamber 137 and the moisture in wick 132 is picked up by themedical gas before it is discharged from housing 135. In this embodimentthe medical gas can be brought to the proper temperature before itenters the system 130. An advantage of this type of wick system,particularly when positioned proximate the point of entry into thepatient, is that if the gas is cooled slightly as it enters the patientany moisture condensation can be absorbed by the wick rather than beingcarried into the patient as liquid droplets. Thus if the temperature ofthe medical gas is at the proper temperature the wick system of FIG. 13can be used to provide moisture to the medical gas or to remove anycondensed liquid. As an alternate the system 130 can be used inconjunction with a heat and exchange tube described herein that may belocated a distance from the patient since the wick can absorb andprevent liquid droplets from entering the patient if any moisturecondenses out of the medical gas as it enters the patient.

Although a permeable membrane has been described for the transfer ofmoisture other liquid barriers that permit water vapor transfer can beused. FIG. 14 is an enlarged portion of porous barrier 140 for use inmedical gas humidification and heat exchange system with the barrierhaving micro pores 143 extending from side 141 of the barrier toopposite face 142 to permit water vapor to pass therethrough.

FIG. 15 is an enlarged view of a non porous barrier 150 for use inmedical gas humidification and heat exchange systems with the non-porousbarrier that permits migration of water vapor through the barrier yetthere are no direct openings in the barrier. Porous barrier 151 has afirst face 152 and a second face 153 which forms a liquid barrier. A setof arrows 154 155 and 156 are shown in a zig zag pattern to illustratethe passing of water vapor from face 152 to face 153.

Thus the present invention includes a method of delivering a medical gasin a conditioned state to a body cavity to avoid or inhibit body traumaby directing a medical gas into a body cavity through a lumen located ona first side of a barrier permeable to water vapor but impermeable toliquid water to thereby transfer water vapor through the barrier andinto the medical gas so that when the medical gas discharges therefromthe humidity of the medical gas is in a conditioned state forinsufflation.

In an alternate embodiment the invention includes an apparatus fordelivering medical gas in a conditioned state to a body cavity with thesystem including, a medical gas; a chamber for holding the medical gas;a source of water located external the chamber for holding the medicalgas and a wick extending into the source of water and into the chamberto permit the wicking of water into the medical gas located therein tobring the medical gas to the proper insufflation humidity.

1. A method of delivering a medical gas in a conditioned state to a bodycavity to avoid or inhibit body trauma comprising; directing a medicalgas into a body cavity through a lumen located on a first side of abarrier permeable to water vapor but impermeable to liquid water;flowing a pre-heated liquid through a lumen located on a second side ofthe barrier in a co-current and countercurrent direction to a flowdirection of the medical gas to transfer heat to the medical gas throughthe barrier and to transfer water vapor from the pre-heated liquid asthe liquid flows therethrough so that when the medical gas dischargestherefrom the humidity and the temperature of the medical gas are in aconditioned state; and monitoring a temperature of the medical gasdischarging therefrom and controlling the heat transfer from the liquidto the medical gas to maintain the medical gas at a constanttemperature.
 2. The method of claim 1 wherein the temperature of themedical gas deliverable to the body cavity is maintained at about 37°centigrade.
 3. The method of claim 1 wherein the relative humidity ofthe gas is maintained in excess of 50% by returning the preheated liquidthrough a further lumen located along another side of the barrier. 4.The method of claim 1 wherein the relative humidity of the gas ismaintained in excess of 96%.
 5. An apparatus for delivering medical gasin a conditioned state to a body cavity comprising; a tube; and a finsupporting a medical gas enclosure in said tube to form a first lumenand a second lumen therein, said first lumen supporting a flow of apreheated liquid in a co-current direction to a flow direction of themedical gas supported by said medical gas enclosure and said secondlumen supporting a flow of the preheated liquid in a countercurrentdirection to said flow direction of the medical gas supported by saidmedical gas enclosure, said medical gas enclosure comprising a barrierpermeable to water vapor but impermeable to liquid water, said barrierforming at least a part of the medical gas enclosure, said barrierhaving a first side proximate said pre-heated water for transfer ofwater vapor from the preheated water to a medical gas on the oppositeside of the barrier to thereby bring the medical gas to a conditionedstate for insufflation.
 6. The apparatus of claim 5 wherein the water isheated to an insufflation temperature to bring the medical gas to a bodydeliverable state through conductive heat transfer through the barrier.7. The apparatus of claim 6 wherein the barrier comprises a tubularmember and the first side comprises a fluid passage internal to thetubular member and the opposite side comprises a fluid passage externalto the tubular member.
 8. The apparatus of claim 7 wherein the tubularmember has a circular cross section.
 9. An apparatus for deliveringmedical gas in a conditioned state to a body cavity comprising; amedical gas conduit having a first lumen supporting a flow of a medicalgas, a second lumen supporting a flow of a preheated liquid in aco-current direction to a flow direction of the medical gas, and a thirdlumen supporting a flow of the preheated liquid in a countercurrentdirection to said flow direction of the medical gas; and a liquid gasseparation barrier having an end located adjacent a body cavity entrydevice, said liquid gas separation barrier having a first side forcontacting the liquid and a second side for contacting the medical gas,said liquid gas separation barrier permitting passage of water vaporinto the medical gas through the liquid gas separation barrier while atthe same time preventing passage of liquid therethrough to thereby bringthe medical gas to a conditioned humidification state for delivery to apatient for surgery insufflation.
 10. The apparatus of claim 9 whereinthe liquid gas separation barrier comprises a diffusion membrane. 11.The apparatus of claim 10 wherein the diffusion membrane is a nonporousmembrane.
 12. The apparatus of claim 10 wherein the diffusion membraneis a hydrophobic membrane.
 13. The apparatus of claim 12 wherein thehydrophobic membrane is selected from the group consisting ofpolyolefin, fluorinated polymers such as tetrafluoroethylene orfluorinated ethylene-propylene, polyetherimide, polysulfone andsilicone.
 14. The apparatus of claim 9 wherein the liquid gas separationbarrier comprises a sheet of material extending between a liquid chamberand a medical gas chamber.
 15. The apparatus of claim 9 wherein theliquid gas separation barrier comprises a hydrophobic material.
 16. Theapparatus of claim 9 wherein the liquid gas separation barrier comprisesa sidewall of a cylindrical tube.
 17. The apparatus of claim 16 whereinthe liquid gas separation barrier comprises a material selected from thegroup consisting of polyvinyl alcohol, cellulose, cellulose derivatives,nylon, polyester, polycarbonate, polysulfone, polyethersulfone,polyimide, silicone and polyurethane.
 18. The apparatus of claim 16including a chamber for receiving a source of water with a heaterlocated in said chamber for heating the water.
 19. The apparatus ofclaim 16 wherein the liquid gas separation barrier comprises acylindrical tube of hydrophobic material.
 20. The apparatus of claim 16wherein the liquid gas separation barrier has pores less than 0.2microns in diameter to prevent passage of bacteria through the liquidgas separation barrier.
 21. The apparatus of claim 16 wherein the wateris in non-dispersive contact with the liquid gas separation barrier.